One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(9,10)(11,16)(12,15)(13,14)(19,23)(22,24)(26,30)(27,33)(32,37)(35,39) involution — undirected(1,2,5,3)(4,6,8,7)(9,11)(10,12)(13,16)(14,15)(18,21)(22,24)(28,36)(32,37)(35,39)(38,40)(2,3)(4,8)(10,13)(12,16)(17,18)(19,22)(20,21)(23,24)(25,26,29,30)(27,34,33,31)(28,32,36,37)(35,40,39,38)(1,3,5,2)(4,7,8,6)(9,12,14,16)(10,15,13,11)(25,27,29,33)(26,31,30,34)(28,35,36,39)(32,38,37,40)(1,4,5,8)(2,6,3,7)(9,13,14,10)(11,16,15,12)(17,19)(18,22)(20,23)(21,24)(25,28)(26,32)(27,35)(29,36)(30,37)(31,38)(33,39)(34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.